How do you import a rigged character from one blender file to another?
You can copy and paste models from one running instance of Blender to another using the same Copy and Paste keyboard shortcuts that work for the majority of software. Ctrl+c and then Ctrl+v.  

The Mac version for these shortcuts is Command+c then Ctrl+v but Blender was programed to also recognize the windows version so usually you can use either for OS X Blender.

Anyways, open the rigged model in a second instance of Blender and select the Object that you want to transfer over to the other scene.  Copy the model using the appropriate shortcut and then move over to the other scene and paste it in.  The rigging should be pulled over with the objects that are parented to it.  The materials will also transfer over with the model.

Here's how it looks.